Thermally developable light-sensitive material with dimercapto substituted tetrazapentalene toners

ABSTRACT

The present invention relates to a thermally developable lightsensitive material comprising: (1) silver salt of benzotriazole; (2) silver halide prepared by reacting an inorganic halide with the silver salt of benzotriazole; (3) a reducing agent; (4) a binder; and (5) a black-toning agent as described in the specification.

D United States Patent 11 1 1111 3,881,938 Masuda et al. 1 1 May 6, 1975 THERMALLY DEVELOPABLE 3.589.901 6/1971 Lyons 96/1 14.1 LIGH'FSENSITIVE MATERIAL WITH 3,615,549 10/1971 Ohyama et al 96/52 3,635,719 1 1972 Ohkubo et a1. 96/1 14.1 DIMERCAPTO SUBST'TUTED 3,645.739 2/1912 0111111190 et a1 96/1 14.1 TETRAZAPENTALENE TONERS 3,832,186 8/1974 Masuda et a1. 96/1 14.1

Inventors: Takao Masuda; Kinji Ohkubo;

Mitsunori Sugiyama; Tadao Shishido,al of Minami Ashigara, Kanagawa, Japan Assignee: Fuji Photo Film Co., Ltd.,

Minami Ashigara, Kanagawa, Japan Filed: Apr. 26, 1973 App]. No; 354,583

Foreign Application Priority Data Apr. 26, 1972 Japan 47-41969 US. Cl. 96/96; 96/52; 96/58;

' 96/1 14.1 Int. Cl. G03c 1/10; G03c 7/00; G03c 1/02 Field of Search 96/96. 52, 58. 114.1

References Cited UNITED STATES PATENTS 7/1969 Morgan et a1. 96/1141 FOREIGN PATENTS OR APPLICATIONS 1,113,155 5/1968 United Kingdom 96/52 Primary ExaminerNorman G. Torchin Asxistant Examiner-Richard L. Schilling Attorney, Agent, or Firm-Sughrue, Rothwell, Mion. Zinn & Macpeak [57] ABSTRACT The present invention relates to a thermally developable light-sensitive material comprising: (1) silver salt of benzotriazole; (2) silver halide prepared by reacting an inorganic halide with the silver salt of benzotriazole; (3) a reducing agent; (4) a binder; and (5) a black-toning agent as described in the specification.

12 Claims, No Drawings 1 THERMALLY DEVELOPABLE LIGHT-SENSITIVE MATERIAL WITH DIMERCAPTO SUBSTITUTED TETRAZAPENTALENE TONERS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally developable light-sensitive material and, more particularly, to a thermally developable light-sensitive material capa ble of providing a black tone image when developed.

2. Description of the Prior Art Heretofore, photographic processes utilizing a silver halide have been practiced most widely, since they provide excellent photographic properties such as sensitivity and gradation as compared with an electrophotographic process or a diazo photographic process.

However, photographic silver halide light-sensitive materials used in such processes must be subjected, after image-wise exposure and development with a developer, to several processing steps such as stopping", fixing, washing and stabilizing," in order to prevent the developed image from becoming discolored or faded under normal light and also to prevent the undeveloped areas (hereinafter referred to as background) thereof from becoming blackened. Therefore, in using such silver halide light-sensitive materials various problems have been encountered, e.g., these processings require much time and effort, there is a danger to humans due to the chemicals handled, and the processing rooms and hands and garments of work ers are stained with the chemicals.

Therefore, it would be very desirable in photographic processes utilizing silver halides to improve the materials so that they could be processed in the dry state without any solution processing and that the processed images would be stable.

Various efforts have so far been made for this purpose. One attempt is a so-called combined fixing and developing process as described in, e.g., U.S. Pat. No. 2,875,048, British Pat. No. 954,453 and West German Pat. No. 1,163,142, wherein the two steps of development and fixing in the conventional silver halide photographic process are combined; another is an attempt to change the wet processing operations in the silver halide photographic process to dry processings, as described in, e.g., West German Pat. No. l,l74,l59 and British Pat. Nos. 943,476 and 951,644; and a further attempt is to use a light-sensitive element containing as a major component a silver salt of a long-chain aliphatic carboxylic acid, e.g., silver behenate, or a silver salt such as the silver salt of saccharin, the silver salt of benzotriazole, etc., and a catalytic amount of a silver halide, as described in Japanese Patent Publication Nos. 4921/68, 4924/68, 26582/69, 18416/70, 12700/70 and 22185/70, British Pat. No. 1,205,500,

filC.

The present invention belongs to the last class described above, wherein the silver salt of benzotriazole and silver halide are incorporated in a photographic light-sensitive material.

However, in the thermally developable light-sensitive materials hitherto suggested, i.e., involving compositions comprising a silver carboxylate such as silver behenate or the silver salt of benzotriazole, a reducing agent and a catalytic amount of silver halide, there cannot be obtained a black tone image. Therefore, in the thermally developable material containing, e.g., silver behenate, phthalazinone is further added to the abovedescribed composition to obtain a black tone image.

However, phthalazinone, which is effective in known compositions containing silver behenate, is not effective in the present invention which contains the silver salt of benzotriazole as an image-forming compound. This fact will be demonstrated by the comparative example given in the Examples described hereinafter.

The use of the silver salt of benzotriazole as an image-forming compound provides various merits such as less thermal fog is formed upon heating unexposed areas due to the excellent thermal stability thereof as compared with silver behenate, and hence an image having good contrast between image areas and the background can be obtained. Therefore, it is desirable in a thermally developable light-sensitive material containing the silver salt of benzotriazole to provide a compound capable of providing a good, black tone image.

SUMMARY OF THE INVENTION According to the present invention, it has been found that a black-tone, developed image can be obtained by using a thermally developable light-sensitive material comprising: (1) the silver salt of benzotriazole; (2) a silver halide prepared by reacting an inorganic halide with the silver salt of benzotriazole; (3) a reducing agent; (4) a binder and (5) at least one compound rep resented by the following general formula:

wherein R and R each represents a hydrogen atom, an alkyl group or a substituted or unsubstituted phenyl group, so as to render the tone of the developed image mainly black.

DETAILED DESCRIPTION OF THE INVENTION Preferred R and R groups are hydrogen, alkyl of 1-4 carbon atoms, phenyl or halogen-substituted phenyl.

A simple test shows how much effect a particular compound of the above-described compound group exerts in a thermally developable light-sensitive material. This test is as follows.

The following ingredients are ball-milled at about 25C under atmospheric pressure for several hours to prepare a dispersion.

Polyvinyl hutyral 6 g Silver salt of benzotriazole 4 g lsopropyl alcohol 40 ml The resulting dispersion is referred to as dispersion A. Dispersion A is then mixed with the following ingredients to prepare a coating composition.

Amount of Dispersion A quantity prepared Methanol solution containing I i; si 5% by weight mercuric bromide 1 L and 8.5% by weight mercuric l iodide l ml c Acetone solution containing 0.2% by weight sensitizing dye. benzoxazolylidenethio C hydantoin l ml Methyl cellosolve solution containing pg; 25% by weight ascorbic acid monopalmij "*3 tate 8 ml Methyl cellosolve solution containing 5% by weight compound to be tested 8 ml COMPOUND 3 1,4-Diethyll ,4-dimethyl-3,6-dimercapto-2.3a,5 ,6a'

tetrazapentalene (m.p.: [91C] The thus obtained composition is applied to a polyethylene terephthalate support in a silver amount of 1.3 on g per in of the support The resulting coating is left to 3\ p dry at about 50 to 70C under atmospheric pressure /C\ until it substantially solidifies. The resulting element is K c SL1 imagewise exposed to tungsten light for 2 minutes, then u I heated at l30"C for 30 seconds by sandwiching the ele HS C N ment between two heated plates.

The color tone of the image obtained is then visually C judged to determine its relative inferiority or superiority. L

Comparing the thus obtained image with that obtained using phthalazinone, a black tone image can be obtained by using the compound of the present inven- COMPOUND 4 tion while only a brown tone image is obtained using phthalazinone. Specific experiments will be shown in l Hf l;% the Examples etrazapenta ene (mp.

Specific examples of compounds suitable for the invention are illustrated below. L 3 J COMPOUND l 3,oDimercapto-1.4-diphenyl-lH,4H-2,3a,5,6aj,' ]l 0 Sn tetrazapentalene (m.p.: [88C) l 40 i s ---Il )1 COMPOUND 5 SH l,4-Di(o-chlor0phenyl)-3,6-dimercaptolH,4H- l; 1'3 5 2.3a,5,oa-tetrazapentalene (m.p.: 226C (d)) 15 u H l 1 6x1 3 6'Dimercapt0- l ,l ,4.4-tetramethyl-2,3a,5,6al tetrazapentalene (m.p.: 178C) 32 COMPOUND 6 1,4-Diethyl3 ,o-dimercapto-1H,4H-2,3a,5,6atetrazapentalene (m.p.: 187C) l,4-Dimethyl-3,6-dimercapto- I H,4H-2,3a,5,6atetrazapentalene (mp: 189C) ln general, the above-illustrated compounds can be synthesized by the process described in Journal of The American Chemical Society, vol. 39, p. 1335 (1917). Specific synthesis examples of the above-illustrated compounds will be described below.

SYNTHESIS EXAMPLE 1 (COMPOUND l) 5 Grams of benzalazine was dissolved in 150 cc of glacial acetic acid, and g of potassium thiocyanate was added thereto. The resulting mixture was heated in a water bath at 90 95C at atmospheric pressure for 30 minutes, then cooled. The crystals formed were filtered out and recrystallized from ethyl alcohol. There was obtained 5 g of crystals having a melting point of 188C.

SYNTHESIS EXAMPLE 2 (COMPOUND 2) 5 Grams of acetoneazine was dissolved in 120 cc of glacial acetic acid, and 10 g of potassium thiocyanate was added thereto. The resulting mixture was heated in a water bath for 1 hour as in Example 1 then cooled. The crystals formed were filtrated out and recrystallized from ethyl alcohol. There was obtained 5 g of crystals having a melting point of 178C.

SYNTHESIS EXAMPLE 3 (COMPOUND 3) l0 Grams of methyl ethyl ketone azine was dissolved in cc of glacial acetic acid, and 20 g of potassium thiocyanate was added thereto. The resulting mixture was heated in a water bath as in Example 1 then cooled. The crystals formed were filtrated out and recrystallized from ethyl alcohol. There was obtained 1 1 g of crystals having a melting point of 191C.

SYNTHESIS EXAMPLE 4 (COMPOUND 4) 6.8 Grams of hydrazine hydrochloride and 19.6 grams of potassium thiocyanate were dissolved in 100 cc of water and, further, 20 cc of glacial acetic acid was added thereto. Thereafter, 17.2 g of valeraldehyde was gradually added dropwise thereto. After the completion of the dropwise addition, the solution was stirred for 2 hours at the same temperature. The crystals formed were filtrated out and recrystallized from g1acial acetic acid. There was obtained 9 g of crystals having a melting point of 174C.

SYNTHESIS EXAMPLE 5 (COMPOUND 5) l4 Grams of 2,2'-dichlorobenza1azine was dissolved in 400 cc of glacial acetic acid, and 10 g of potassium thiocyanate was added thereto. The resulting mixture was heated for 30 minutes in a water bath as in Example 1 then cooled. The crystals formed were filtered out and recrystallized from ethyl alcohol. There was obtained 9 g of crystals having a decomposition point of 226C.

SYNTHESIS EXAMPLE 6 (COMPOUND 6) 104 Grams of hydrazine hydrochloride and 196 g of potassium thiocyanate were dissolved in 500 cc of water, and cc ofglacial acetic acid was added thereto. Thereafter, 1 16 g of propylaldehyde was gradually added dropwise thereto while stirring under cooling with ice. After the completion of the dropwise addition, stirring was continued for a further 2 hours under cooling with ice. The crystals formed were filtrated out and recrystallized from a mixed solvent of methanol and water. There were obtained g of crystals having a melting point of 186 187C.

SYNTHESIS EXAMPLE 7 (COMPOUND 7) 21 Grams of hydrazine hydrochloride, 39 g of potassium thiocyanate and 50 cc of glacial acetic acid were added to 200 cc ofwater and stirred under cooling with ice. To this was gradually added dropwise 18 g of acetaldehyde. After the completion of the dropwise addition, the solution was stirred for a further 2 hours under cooling with ice. The crystals formed were filtrated out and recrystallized from alcohol. There were obtained 23 g of crystals having a melting point of 189C.

The compound(s) of the present invention used as a black-toning agent can most suitably be added in an amount of from 0.0001 to 1 mol, preferably 0.001-05 rnol, per 1 rnol of the silver salt of benzotriazole. The amount varies depending upon the kind of the compound used, the various ingredients contained in the light-sensitive material, the processing temperature and the like, so the above range is not per se limitative. but by operation in the above range, especially in the preferred range, these factors are taken into account.

As will be apparent to one skilled in the art, mixtures of compounds within the above general formula can be used with equal success. When used, the total amount of all compounds preferably, of course, falls within the above range.

The silver salt of benzotriazole used in this invention is a silver salt insensitive to light, which can be reduced with a reducing agent to provide a silver image only at the areas where exposed silver halide is present and only when heated. The absolute amount of the silver salt of benzotriazole can vary widely, so long as an image of acceptable density for the use involved is obtained. Considering the rather wide differences in visual sensitivity of average users, it is best to have the silver salt of benzotriazole present in an amount of from about 0.3 g/m to about 3 g/m, more preferably 0.5 g/m to 2 g/m, this latter figure being influenced by the relatively high cost of the silver salt. When the particle size of the silver of benzotriazole is 0.01 p. 541., preferably 0.1a 3n, extremely clear images are obtained. This range is not limitative because, obviously, the clarity density will vary from user to user.

As is described above, as the reducing agent used in the invention, those which are capable of reducing the silver salt of benzotriazole in the presence of exposed silver halide upon heating to form a silver image must be used. However, as has already been stated, the silver salt of benzotriazole is more stable than silver behenate and is therefore difficult to reduce by heating. Therefore, even when a reducing agent for silver behenate, such as a bisphenol, is used for the silver salt of benzotriazole, the silver salt of benzotriazole is difficult to reduce due to the weak reducing capability of such a reducing agent.

However, it has already been found that ascorbic acid and/or a derivative thereof serves as a reducing agent effective for the silver salt of benzotriazole. For example, see Japanese Patent Publication No. 22185/70. Examples of effective derivatives of ascorbic acid include monoor dialiphatic esters of ascorbic acid, e.g., the monolaurate, monomyristate, monopalmitate, monostearate, monobehenate, dilaurate, dimyristate, dipalmitate, distearate and dibenhenate, etc., of ascorbic acid. Generally, C -C carbon atom groups are preferred as the aliphatic moiety to forming an ester structure. In addition, D-araboascorbic acid is also suitable for the invention as a good reducing agent.

As another group of reducing agents suitable for the invention, there are illustrated 3-pyrazolidone derivatives. That is, effective 3-pyrazolidone derivatives include l-phenyl-3-pyrazolidone, l-phenyl-4-methyl-3- pyrazolidone, 1-p-methyl-phenyl-3-pyrazolidone, 1- phenyl-S carboxy-3-pyrazolidone, l-phenyl-4,4- dimethyl-S-pyrazolidone, l-phenyl-5-carboxyethyl-3- pyrazolidone, and 1-phenyl-S-methyl-3-pyrazolidone,

etc.

Preferred ascorbic acid derivatives are the monoor dicarboxylate of ascorbic acid, and preferred 3- pyrazolidone derivatives are those substituted with alkyl having 1-4 carbon atoms, carboxyalkyl having 1-5 carbon atoms or substituted l-aryl-3- pyrazolidones.

If desired, combinations of ascorbic acid and derivatives thereof, combinations of 3-pyrazolidone derivatives, or combinations of ascorbic acid or derivatives thereof and B-pyrazolidons derivatives can be employed.

The reducing agent in the present invention can most suitably be added in an amount of 0.1-5 mols per 1 mol of silver salt of benzotriazole.

As has already been stated, the silver halide used in the invention is prepared by reacting an inorganic halide with the silver salt of benzotriazole to react with a part of the silver salt of benzotriazole, thereby forming silver halide. For example, as in the testing method previously stated, silver halide can be produced by merely adding a solution of inorganic halide, e.g., mercuric bromide and/or mercuric iodide, to a polymer disper' sion of the silver salt of benzotriazole. The formation of silver halide by the reaction between a part of the silver salt of benzotriazole and these halides is apparent from, e.g., an examination of the change in the X-ray diffration pattern of the system. The conditions of reac tion are not overly critical since this reaction proceeds rather easily, and the reaction is usually at atmospheric pressure at mild temperatures, e.g. 20-60C. In practice, the solution of inorganic halide is merely added to a polymer dispersion of the silver salt of benzotriazole and the system agitated for 5 minutes.

Examples of suitable inorganic halides are those represented by the formula M Xn where M is a cation, e.g., H, NH}, or a metal, X is Cl, Br, 1', and n is the valence of M. Specific examples include hydrogen bromide, hydrogen iodide, ammonium bromide, ammonium iodide, ammonium chloride, metal halides such as the chloride, bromide or iodide of metals such as strontium, cadmium, zinc, chromium, sodium, potassium, barium, iron, cesium, lanthanum, copper, nickel, magnesium, aluminum, antimony, cobalt, mercury, lead, beryllium, lithium, calcium, tin, gold, manganese, indium, rhodium, ruthenium, palladium, osmium, iridium, platinum, thallium, bismuth, etc.

The inorganic halides are most suitably added in an amount of 1/1000 to 0.5 mol per 1 mol of silver salt of benzotriazole. The reaction with the silver salt of benzotriazole is substantially stoichiornetric. So, 1/100 mol of inorganic halide of an appropriate valence will yield 1/100 mol of silver halide.

The thermally developable light-sensitive material compositions used in the practice of the invention are incorporated in a binder. Any binder can be used which is at least semi-transparent so that the exposure light reaches the thermally developable substance, which is not degraded at the exposure or heating conditions and which serves as a good dispersing material. Suitable binders are usually hydrophobic, but hydrophilic ones can also be used. These are transparent or semitransparent, and include natural substances such as gelatin, gelatin derivatives, cellulose derivatives, and synthetic polymer materials such as polyvinyl compounds, acrylamide polymers, etc. Other usable synthetic polymer compounds include latex-type dispersions of one or more vinyl compounds. Preferred high molecular weight materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, polyvinyl pyrrolidone, ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubbers, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, vinyl acetate-vinyl chloride-maleic acid copolymers and polyvinyl alcohol.

These binders are most suitably added in a propor tion of 4:1 to 1:4 (weight ratio to the silver salt of benzotriazole As the support used in the practice of the invention for the thermally developable light-sensitive materials described in this specification, a wide variety of supports can be used. Examples of typical supports are cellulose nitrate films, cellulose ester films, polyvinyl acetal films, polystyrene films, polyethylene terephthalate films, polycarbonate films, other resinous materials, glass, paper, metal and the like.

Simply stated, any support can be used in the present invention which adheres well to the thermally developable substance and which is not harmfully degraded at the exposing or developing conditions.

1n the thermally developable light-sensitive material used in the practice of the present invention there may be provided an antistatic layer or an electroconductive layer. An antihalation substance and an antihalation dye may also be incorporated in the thermally developable light-sensitive material composition, if desired.

If desired, in the thermally developable material used in the practice of the invention there may further be incorporated a matting agent such as starch, titanium oxide, silica, etc., and/or a fluorescent brightening agent such as a stilbene, triazine, oxazole or coumarin fluorescent brightening agent. or the like.

The thermally developable light-sensitive layer used in the practice of the invention may be coated by various coating methods including an immersion method, air-knife method, curtain-coating method and an extru sion coating method using a hopper as described in US. Pat. No. 2,681,294. If desired, two or more layers may be coated at the same time.

While not overly critical, best results are obtained when the light sensitive layer of the present invention has a thickness of from about lp. to about 20p, preferably 3a a. The use of a thickness of at least 1p gives sufficient strength to the element for normal handling, and the use ofa thickness greater than p provides no results better than a thickness of 20p This range is provided primarily considering mechanical factors, and it is not limitative on the concept of the invention.

Optically sensitizing dyes may advantageously be used to impart light sensitivity to the element used in the practice of the invention. For example, the element may be optically sensitized by adding a sensitizing dye in the form of a solution in an organic solvent or a dispersion. As usable optical sensitizing agents, there are illustrated cyanine dyes, merocyanine dyes, etc.

After imagewise exposure to a light source such as a xenon lamp, tungsten lamp, mercury lamp, etc., latent images formed in the light-sensitive layer of the abovedescribed thermally developable light-sensitive material can be developed merely by heating the element. Therefore, another embodiment of the invention relates to a process for developing the latent image formed in the light-sensitive layer of the exposed thermally developable light-sensitive material by heating to about 100 to l60C until the desired image is devel oped.

A suitable development temperature is 100 to 160C and. usually, a temperature of 110 to 140C is em ployed. By prolonging or shortening the heating period, higher or lower temperature may be employed within the above range. A developed and stable image can usually by obtained in 1 second to 60 seconds.

As the means to provide the necessary heating, various means may be employed. The above-described ele ment can be brought into contact with simple heating plates, etc., or may be brought into contact with a heated drum, or, in some cases, the element may be passed through a heated space or subjected to high frequency induction heating.

Having thus described the invention generally, the following specific examples of preferred embodiments of the invention are offered to illustrate the same in greater detail.

EXAMPLE 1 Dispersion A heretofore identified was prepared in the manner described before. Dispersion A was mixed for 4 hours in a ball mill. Thereafter, dispersion A was mixed with the following ingredients to prepare the following composition.

Dispersion A in an amount of mixed with: 40 ml Methanol solution containing 5% by weight mercuric bromide and 8.5% by weight mercuric iodide 1 ml at 50C Acetone solution containing l atmosphere 0.2% by weight sensitizing dye, pressure, benzoxazolylidenethiohydantoin 1 ml Each solution Methyl cellosolve solution con is added taining 25% by weight ascorbic over an acid monopalmitate 8 ml interval of 5 minutes. Methyl cellosolve solution con- (in sequence) taining 1% by weight Compound 1 earlier described 5 ml The thus obtained composition was applied to a polyethylene terephthalate film at 50C at a wet thickness of a. The resulting coated film was dried at 70C for 1 hour to prepare a thermally developable lightsensitive material.

Then, the resulting material was exposed 10 lux) to tungsten light for 2 minutes through a transparent neg ative original having a varying gradation, and heated for 30 seconds by sandwiching it between metallic plates heated to C. There was thus formed a black tone positive image having a gradation corresponding to that of the original.

A control element was prepared in the same manner as above except for omitting Compound 1. and exposed and processed in the same way. The thus obtained image had a yellowish brown tone and showed only an extremely low image density.

Separately, an element was prepared in the same manner except using phthalazinone instead of Compound l in the same amount which element was then exposed and processed as above. The thus obtained image has a brown tone and showed only a low image density.

Furthermore, an element was prepared as above using 3-mercapto4-phenyl-l,2,4-triazole used by the inventors as a toning agent (see Japanese Patent Publication Nos. 18416/70, 12700/70 and 26582/69) instead of Compound 1 in the same amount, and then exposed and processed as above. The thus obtained image had a brown tone, though a little blackish, and showed a low image density.

Still further, an element was prepared using 1,3- diphenylguanidine used by the inventors as a toning agent (see Japanese Patent Publication No. [2700/70) instead of Compound 1 in the same amount, and exposed and processed as above. The thus obtained image showed a good image density. though it had a blackish brown tone.

From the above experimental data, the following is apparent: phthalazinone, which is effective for a silver behenate system, is ineffective for a silver salt of benzo triazole system, and the toning agent in accordance with the present invention provides still yet a better black-tone image than is provided by conventional toning agents (i.e., 3-mercapto-4-phenyl-l,2,4-triazole, LB-diphenylguanidine, etc.) effective for a silver salt of benzotriazole system.

EXAMPLE 2 The procedures described in Example l were repeated except for using Compound 2 instead of Compound l in the same amount. A good image with black tone as in Example 1 was obtained.

EXAMPLE 3 The procedures described in Example 1 were repeated except for using Compound 3 instead of Compound l in the same amount. There was obtained a good image with black tone as in Example 1.

EXAMPLE 4 EXAMPLE 5 The procedures described in Example I were repeated except for using Compound 6 instead of Compound in the same amount, There was obtained a good image with black tone as in Example l.

EXAMPLE 6 The following ingredients were mixed to prepare a composition.

gradation. The material was then heated for 30 seconds by sandwiching it between metallic plates heated to l30C. There was obtained a positive black tone image having gradation corresponding to that of the original.

EXAMPLE 7 The procedures described in Example 6 were conducted except for using Compound 7 in place of Compound 4 in the same amount. There was obtained a black tone image as in Example 6.

EXAMPLE 8 The following ingredients were mixed to prepare a composition.

The thus obtained composition was applied to a polyethylene terephthalate film support at C in a wet thickness of 80a. The resulting coated film was dried at 70C for 20 minutes. Thereafter, the following ingredients were mixed to prepare a composition.

Vinyl chloride-vinyl acetate copolymer (85:15 by weight ratio) Tetrahydrofuran l5 g l00 ml The resulting composition was top-coated on the above film at 50C in a wet thickness of p, then dried at 70C for 1 hour.

The thus prepared thermally developable lightsensitive material is more preferred as a second original The thus obtained composition was applied to a polyethylene terephthalate film support at 50C in a wet thickness of 8011.. The resulting coated film was dried at 70C for 1 hour to prepare a thermally developable light-sensitive material. Thereafter, this material was exposed to a xenon flash lamp for 10' l0 lux) second through a transparent negative original having varying as compared with a light-sensitive material having no top-coating layer, due to an increase in the transparency of the coated layer thereof.

This material was then exposed to a tungsten lamp (contact printed at 10,000 lux) for 30 seconds through a transparent negative original having varying gradation, then heated for 20 seconds by sandwiching it be- EXAMPLE 9 The procedures described in Example 8 were conducted except for using, as a reducing agent, a mixture of 2 g of ascorbic acid monostearate and 0.2 g of l-phenyl-3-pyrazolidone instead of ascorbic acid monomyristate. There was obtained an image of black tone as in Example 8 and, by heating at 120C for 10 seconds, the same maximum image density as in Example 8 was obtained.

EXAMPLE 10 The procedures described in Example 8 were conducted except for using the following dispersion B instead of dispersion A. Preparation of dispersion B:

Each of the following ingredients was ball-milled for 4 hours at about 25C under atmospheric pressure.

Ethyl cellulose Silver salt of benzotriazole lsopropyl alcohol 4 BMW There was obtained a black tone image as in Example 9.

EXAMPLE ll The following ingredients were mixed to prepare a composition.

through a transparent negative original having varying gradation. Thereafter, the material was heated for 15 seconds by sandwiehing it between metallic plates heated to l l0C. There was obtained an image of black tone.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

l. A thermally developable light-sensitive material comprising a support having thereon a layer comprising: (1) silver salt of benzotriazole; (2) silver halide formed by reacting an inorganic halide with said silver salt of benzotriazole: (3) a compound selected from the group consisting of ascorbic acid, derivatives thereof and 3-pyrazolidone derivatives. as a reducing agent; (4) a binder; and (5) one or more compounds represented by the general formula:

Dispersion A ml Methanol solution containing 5% by weight ammonium bromide l ml pressure Acetone solution containing 0.2% by weight sensitizing dye. bcnzoxazolyidenethiohydantoin 1 ml Example l Methyl ccllosolvc solution containing 25% by weight ascorbic acid monopalmitate Methyl cellosolvc solution containing l /r by weight Compound 3 Acetone dispersion containing 15: by weight zinc oxide 4 ml Each solution is added over an interval of 5 minutes as in at C,] atmosphere 3. A thermally developable light-sensitive element as claimed in claim 2 wherein the silver salt of benzotriazole is present in an amount of from about 0.3 to about 4. A thermally developable light-sensitive element as claimed in claim 3 where the reducing agent is present in an amount of from 0.] to mols per mol of the silver salt of benzotriazole and the silver halide is present in an amount of from 1/1000 to 0.5 mol per mol of the silver salt of benzotriazole.

5. A thermally developable light-sensitive element as claimed in claim 4 where the binder is present in a proportion of 4:1 to I14 (weight ratio to parts of silver salt of benzotriazole).

6. A thermally developable light-sensitive element as claimed in claim 5 where in the compound R and R is hydrogen, C C, alkyl, phenyl or halogen substituted phenyl.

7. A thermally developable light-sensitive element as claimed in claim 6 where the inorganic halide is of the formula MX, where M is hydrogen, ammonium or a metal, X is chloride, bromine or iodine and n is the valence of M.

8. A thermally developable light-sensitive element as claimed in claim 7 where M is hydrogen, ammonium, mercury, osmium, calcium, tin, gold, manganese, gallium, indium, rhodium, ruthenium, palladium, iridium, platinum, thallium, or bismuth.

9. A thermally developable light-sensitive element as claimed in claim 7 where the reducing agent is ascorbic acid or the monolaurate, monomyristate, monopalrnitate, monostearate, monobehenate, dilurate, dimyristate. dipalmitate, distearate, and dibehenate of ascorbic acid. l-phenyl-3-pyrazolidone, l-p-methylphenyl- 3 -pyrazolidone, l-phenyl-5-carboxy-3-pyrazolidone, l-phenyl-4,4-dimethyl-3pyrazolidone, l-phenyl-S- carboxyethyl-3-pyrazolidone, and l-phenyl-S-methyl- 3-pyrazolidone.

10. A thermally developable light-sensitive element as claimed in claim 8 where the reducing agent is ascorbic acid or the monolaurate, monomyristate, monopalmitate, monostearate, monobehenate, dilurate, dimyristate, dipalmitate, distearate, and dibehenate of ascorbic acid, l-phenyl-3-pyrazolidone, l-phenyl-4- methyl-3-pyrazolidone, 1-p-methylphenyl-3- pyrazolidone, l-phenyl-S-carboxy-3-pyrazolidone, lphenyl-4,4-dimethyl-3-pyrazolidone, l -phenyl-5- carboxyethyl-3-pyrazolidone, and l-phenyl-S-methyl- 3-pyrazolidone.

ll. A thermally developable light-sensitive element as claimed in claim 10 where the compound is selected from Compounds 1-7 below:

COMPOUND l 3,6-Dimercapto-l ,4-diphenyllH,4H-2,3a,5,6atetrazapentalene (m.p.: l88C) COMPOUND 2 3,6-Dimercapto-1,l ,4,4-tetramethyl-2,3a.5 ,6atetrazapentalane (m.p.: 178C) COMPOUND 3 l ,4-Diethyl-1,4-dimethyl-3 ,6-dimercapto-2,3a,5,6atetrazapentalene (m.p.: 191C) l ,4-Dibutyl-3,fi-dimercaptol H,4l-l-2,3a,5,6atetrazapentalene (m.p.: l74C) COMPOUND 5 l.4-Di(o-chlorophenyl)-3,6-dimercaptol H.4H- 2,3a,5,6l,4-Di(o-chlorophenyl)-(m.p.: 226C (d)) A COMPOUND 7 l l,4-Dimethyl-3,6-dimercaptl H,4H-2,3a,5,6a- M tetrazapentalene (m.p.: 189C) 0 vi i. t: SE a l l I n C l I: 4 a

k l0 T1 l C19 HS C l \fi/ COMPOUND 6 ii CL l,4-Diethyl-3,6-dimercapto-lBAH-2,321,162!- tetrazapentalene (m.p.: l87C) 12. A thermally developable light-sensitive element D 2 as claimed in claim 7 where the silver salt of benzotriazole has a particle size of 0.0];L to 5;!" N I; S11 1 l H l l and s c 3: N u C/ Pi C -55 a= 

1. A THERMALLY DEVELOPABLE LIGHT-SENSITIVE MATERIAL COMPRISING A SUPPORT HAVING THEREON A LAYER COMPRISING- (1) SILVER SALT OF BENZOTRIAZOLE; (2) SILVER HALIDE FORMED BY REACTING AN INORGANIC HALIDE WITH SAID SILVER SALT OF BENZOTRIAZOLE: (3) A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ASCORBIC ACID, DERIVATIVES THEREOF AND 3-PYRAZOLIDONE DERIVATIVES, AS A REDUCING AGENT; (4) A BINDER; AND (5) ONE OR MORE COMPOUNDS REPRESENTED BY THE GENERAL FORMULA:
 2. A thermally developable light-sensitive element as claimed in claim 1 wherein the compound of the present invention is present in an amount of from 0.001 to 1 mol per mol of silver salt of benzotriazole.
 3. A thermally developable light-sensitive element as claimed in claim 2 wherein the silver salt of benzotriazole is present in an amount of from about 0.3 to about 3 g/m2.
 4. A thermally developable light-sensitive element as claimed in claim 3 where the reducing agent is present in an amount of from 0.1 to 5 mols per mol of the silver salt of benzotriazole and the silver halide is present in an amount of from 1/1000 to 0.5 mol per mol of the silver salt of benzotriazole.
 5. A thermally developable light-sensitive element as claimed in claim 4 where the binder is present in a proportion of 4:1 to 1:4 (weight ratio to parts of silver salt of benzotriazole).
 6. A thermally developable light-sensitive element as claimed in claim 5 where in the compound R1 and R2 is hydrogen, C1 - C4 alkyl, phenyl or halogen substituted phenyl.
 7. A thermally developable light-sensitive element as claimed in claim 6 where the inorganic halide is of the formula MXn where M is hydrogen, ammonium or a metal, X is chloride, bromine or iodine and n is the valence of M.
 8. A thermally developable light-sensitive element as claimed in claim 7 where M is hydrogen, ammonium, mercury, osmium, calcium, tin, gold, manganese, gallium, indium, rhodium, ruthenium, palladium, iridium, platinum, thallium, or bismuth.
 9. A thermally developable light-sensitive element as claimed in claim 7 where the reducing agent is ascorbic acid or the monolaurate, monomyristate, monopalmitate, monostearate, monobehenate, dilurate, dimyristate, dipalmitate, distearate, and dibehenate of ascorbic acid, 1-phenyl-3-pyrazolidone, 1-p-methylphenyl-3-pyrazolidone, 1-phenyl-5-carboxy-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 1-phenyl-5-carboxyethyl-3-pyrazolidone, and 1-phenyl-5-methyl-3-pyrazolidone.
 10. A thermally developable light-sensitive element as claimed in claim 8 where the reducing agent is ascorbic acid or the monolaurate, monomyristate, monopalmitate, monostearate, monobehenate, dilurate, dimyristate, dipalmitate, distearate, and dibehenate of ascorbic acid, 1-phenyl-3-pyrazolidone, 1-phenyl-4-methyl-3-pyrazolidone, 1-p-methylphenyl-3-pyrazolidone, 1-phenyl-5-carboxy-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 1-phenyl-5-carboxyethyl-3-pyrazolIdone, and 1-phenyl-5-methyl-3-pyrazolidone.
 11. A thermally developable light-sensitive element as claimed in claim 10 where the compound is selected from Compounds 1-7 below: COMPOUND 1 3,6-Dimercapto-1,4-diphenyl-1H,4H-2,3a,5,6a-tetrazapentalene (m.p.: 188*C)
 12. A thermally developable light-sensitive element as claimed in claim 7 where the silver salt of benzotriazole has a particle size of 0.01 Mu to 5 Mu . 